Expansible combustion heater unit and support therefor



June 25, 1957 J. R. PINKUS ETAL EXPANSIBLE CGMBUSTION HEATER UNIT AND SUPPORT THEREFOR Filed Aug. 2, 1952 f/vvewroias; (/EROME A. Puvxus- P/c/m/w d. P575255 United States Patent EXPANSIBLE COMBUSTION HEATER UNIT AND SUPPORT THEREFOR Jerome R. Pinkus, Los Angeles, and Richard J. Petersen, Downey, Calif., assignors to Utility Appliance Corp., Los Angeles, Calif., a corporation of California Application August 2, 1952, Serial No. 302,294

8 Claims. (Cl. 126-99) This invention relates to improvements in space heaters conventionally utilized in heating the air in homes and other structures and, more particularly, to a heater of the aforementioned character having incorporated therein a heater unit, comprising a combustion chamber and a heat exchanger unit, the heater unit being supported upon the frame of the heater in such a manner as to effectively accommodate expansion stresses set up in the heater unit by the creation of products of combustion in the combustion chamber and to accommodate stresses which would tend to cause the separation of said unit from said frame due to expansion of said unit with respect to said frame.

While our invention is particularly applicable to space heaters in which the combustion chamber and heat exchanger are formed integrally and will be so described, it is obvious that the principles of our invention may be applied with equal cogency to heat exchangers wherein the combustion chamber and heat exchanger are formed separately but are secured to each other in such a manner as to constitute a unitary structure subject to the same deficiencies as conventional heater units wherein the combustion chamber and heat exchanger are formed integrally.

It is generally the practice, in the manufacture of space heaters designed for use in dwellings and other structures having a relatively limited cubic footage, to provide heater units which are formed of sheet metal and which provide a unitary structure consisting of a combustion chamber and the heat exchanger associated therewith. These heater units are usually formed of relatively heavy gage sheet metal in two half-shells which are subsequently secured at mating edges to each other by means of welding or any other similar means of securement and are subsequently mounted on supporting frames in the interior of the space heaters by the securement of at least their forward or rearward edges to said frames.

When the heater unit is utilized and products of combustion are formed in the combustion chamber, they flow through the heat exchanger portion of the structure and the sheet metal of which the heater unit is formed expands proportionally with the intensity of the heat to which it is subjected. However, since the most intense heat is experienced in the combustion chamber and the intensity of the heat falls olf as the products of combustion are translated through the heat exchanger portion of the heater unit, differential expansion between various areas of the heater unit occurs and, in conventional heater unit structures, results in the warping of the metal from which the heater unit is formed and ultimately in the breaking of the joints between the mating flanges of the shells of the heater unit due to the imposition of shear loads thereupon occasioned by the ditferential expansion of the metal of the unit.

When such shearing of the securement of the mating flanges of the shells of the heater unit occurs, the creation of openings in the unit permits leakage of the products of combustion together with dangerous gases and may result in conditions which are hazardous to both life and property.

It is, therefore, an object of our invention to provide a heater unit for a space heater which includes a combustion chamber and a heat exchanger connected to each other in such a manner that expansion of the material from which the heat exchanger and combustion chamber are formed would result in warpage of the joints between the heat exchanger and combustion chamber shells, were it not that said unit includes an expansion space designed to accommodate expansion in the material of the heat exchanger and combustion chamber and thus to eliminate stresses in the structure of the heater unit which would ultimately result in shearing of the joints maintaining the component portions of the heater unit in operative relationship with each other.

Another object of our invention is the provision of a heater unit which is constituted by 'a unitary combustion chamber-heat exchanger structure formed of sheet metal and provided with an expansion space designed to accommodate loads resulting from the dilferential expansion in the heater unit occasioned by unequal distribution of heat throughout the unit.

In fabricating space heaters of the type under consideration, one or more heater units are located in the interior of a cabinet or other housing, the heater units being supported on a substantially rigid supporting frame within the cabinet. Obviously, when expansion occurs in the heater units, stresses are exerted upon the units due to the affixation of the units at spaced points to the frame and the stresses between such spaced points frequently result in the breaking loose of the heater units from their points of securement to the frame or in the rupture of the units themselves, thus permitting gases and products of combustion to leak through openings created by such rupture. The relatively large loads imposed upon the points of attachment of the heater unit to the frame result primarily from the fact that, while the heater unit is subjected to relatively high temperatures, the frame to which it is aflixed is not subjected to such temperatures and the expansion of the unit is not accompanied by any substantial expansion of the frame.

A further object of our invention is the provision of a heater unit which is formed of sheet metal and which includes a structure consisting of a unitary combustion chamber and heat exchanger, said structure being fastened to the frame of the heater in which it is incorporated at spaced points, one end of the structure being stressed prior to its afiixation to the frame in a direction away from the other end of the structure, which has been previously secured to the frame, in order that subsequent stresses induced in the structure by expansion, due to heat, may be accommodated by the initial stress imposed upon the structure during the afiixation thereof to said frame so that said unit will not tear away from or buckle on said frame.

Another object of our invention is the provision of a heater unit of the aforementioned character which includes an expansion space and which is prestressed in the aforementioned manner prior to its complete .aflixation to the frame of the heater so that expansive stresses may be accommodated by both the prestressing of the structure and the provision therein of the expansion space, thereby permitting expansion loads to be accommodated by both means for the elemination of expansive stresses induced in said structure. Other objects and advantages of our invention will be apparent from the following specification and the accompanying drawing, which is for the purpose of illustration only, in which:

Fig. 1 is a perspective, partly sectional view of a space heater incorporating a heater unit constructed in accordance with our invention;

Fig. 2 is a partly side elevational, partly sectional view of a portion of a heater unit constructed in accordance with our invention; and i Fig. 3 is an enlarged, fragmentary sectional view taken on the broken line 33 of Fig. 2. Referring to the drawing, and particularly to Fig. 1 thereof, we show a space heater which is housed in a cabinet 11 which is provided with a warm air discharge opening 12 at the top thereof adapted to discharge heated air into ducts or other distribution means connected with the room spaces to be heated by the space heater l0.

Disposed interiorly of the cabinet 11, adjacent the fnont panel 14 of said cabinet, is an elongated, vertically oriented frame member 15 which is constituted by a relatively rigid sheet 16 of metal and which is designed to support a plurality of heater units 18 constructed in accordance with the principles of our invention. Each heater unit 18 is formed of sheet metal of relatively heavy gage and is constituted by two shells 19 and 20 which are provided at their edges with peripheral flanges 21 and 22, respectively, adapted to be secured to each other bymeans of welding, or any other similar fastening means, to provide a unitary structure constituting a combustion chamber portion 24 anda heat exchanger portion 25. The heat exchanger portion 25 is formed integrally with the combustion chamber 24 and the walls thereof, as best seen in Figs. 1 and 2 of the drawing, are provided with longitudinal corrugations 27 which materially increase the area of the heat exchanger walls and also increase the elfectiveness with which heat energy can be transmitted from the heat exchanger to a blast of air passing thereover.

Formed integrally with the upper end of the heat exchanger portion 25 of the heater unit 18 and constituting a portion thereof is an elongated tubular duct 29 which communicates at its outer end with a vent connection 29a.

In conventional heater unit constructions the tubular duct 29 is not only integrally formed with the heat exchanger portion 25 of the heater unit 18, but is connected'thereto throughout its entire length. However, to overcome stress resulting from the expansion of the walls of the heater unit 18 due to the passage of products of combustion therethrough, We prow'de an expansion space 30 in the heater unit 18 which extends substantially transversely thereof and which is so dimensioned that it will accommodate, to a certain extent, or entirely if desired, expansive stresses incurred by the heater unit. due to the expansion of the metal from which it is constituted when the products of combustion flow therethrough.

The heater unit 18 is secured, as best shown in Fig. 2 of the drawing, adjacent its lower end to the frame member 15, as at 32, while at the upper end thereof it is secured by means of the end of the duct 29 to a collar 33 formed in the frame member 15. Although the heater unit 18 is shown as fixed in particular fashion to the frame member 15, it is obvious that any conventional means of affixing the heater unit 18 to the frame member 15 can be utilized. Furthermore, although the heater unit is shown as oriented in vertical position, it is conceivable that i't'cmight be disposed in any one of a number ofother positions such as a horizontal, or inclined, position, a vertical unit being disclosed and discussed in the present instance for purpose of convenience only.

In securing the heater unit 18 to the frame member 15, the lower portion thereof is first secured to the frame member 15 as at 32. Subsequently and prior to the aflixation of the upper end of the heater unit 18, as constituted by the tubular duct 29 of the heat exchanger portion 25 of the heater unit, to the frame member 15, the duct 29 is forced upwardly to bring its end into the collar 33, thus prestressing the heater unit 18 in a vertical direction. The end of the duct 29 is then secured in the collar 33 to maintain the heater unit 18 under stress. e

As indicated in Figs. 2 and 3 of the drawing, and par- V 4 ticularly Fig. 3 which is drawn approximately to scale, if it be assumed that the original vertical dimension of the expansion space 30 in the heat exchange portion 25 of the heater unit 18 is approximately 1 of an inch and that the longitudinal centerline of the expansion space is yy, the upward deflection of the outermost end of the tubular duct 29 will be an additional A of an inch as indicated at x, the original vertical'dimensions a, b' of the expansion space 30 being increased to this extent and a substantial load thus being imposed upon the entire heater unit to develop stresses therein.

Disposed in the combustion chamber portion 24 of the heater unit 18 is a heating element 35 which, when ignited, burns gas or other fuel at elevated temperatures to create products of combustion which flow upwardly through the combustion chamber portion 24 and into and through the heat exchanger portion 25 and ultimately through the tubular duct 29 to the vent 29a. Since the wall area of the heater unit 18 which constitutes the combustion chamber portion 24 of the unit is more directly exposed to the heat energy generated by the heating element 35 than is the wall area of the exchanger portion 25, the expansion of the lower portion of the heater unit is much greater than that of the upper portion thereof, the expansion falling oif progressively until the top of the heater unit adjacent the tubular duct 29 is reached. Therefore, differential expansion exists between the heater unit and the frame member 15 and also between the various areas of the heater unit and since it is restrained by its connection at the upper and lower ends, loads indicated by the arrows 40 of Fig. 2 tend to be induced in the heater unit structure. The most important consideration, however, is the fact that the unit 18 is rigidly secured at spaced points to the frame member 15 so that when expansion occurs in the unit, due to the generation of heat therein, the difierential expansion between the unit 18 and the frame member 15 is accommodated by the prestressing of the unit 18 and the provision of the expansion space 30.

For instance, when expansion occurs in the unit 18, the opposite ends thereof tend to be shifted spatially in directions away from each other, as indicated by the arrows 51 and 52. On conventional heaters the unit, because of its positive afiixation to the frame and the lack of means for accommodating the shear loads imposed on the opposite ends thereof at the points of aifixation to the frame, is frequently buckled or torn from the frame. In applicants heater construction the expansion of the unit occurs but the pretensioning thereof on the frame member 15 prior to its aflixation thereto and the provision of the expansion space 30cause the expansion of the unit 18 to be accommodated and eliminate the loads encountered in conventional heaters.

In other words, since the lower portion of the heater unit 18 expands at a greater rate and to a greater extent than the frame member 15 or the upper portion of the heater unit, and since both ends thereof are restrained by the positive connection of the ends to the frame member 15, the heater unit 18, if of conventional structure, would tend to buckle and induce shear loads in the mating flanges 21 and 22 with the subsequent rupture of said flanges or with a possibility that the heater unit itself might be torn loose from one or more points of attachment with the frame member 15. However, with the construction of our invention, such possibilities are eliminated because when differentialexpansion in the heater unit takes place it is absorbed by the combined action of the expansion space and the prestressing of the unit. The expansion space 30 may be dimensioned for different size heater units to accommodate calculated stresses which will be experienced under all conditions of use and it is not intended that the expansion space be limited to any particular size.

For example, since the upper end of the heater unit is placed under stress by the upward deflection of the outerend of the tubular duct 29 by the distance x to place the entire heater unit under stress, especially along that edge thereof which is fixedly connected to the supporting frame 15, when differential expansion occurs in the heater unit 18, it is accommodated readily since the upward movement of the main portions of the heater unit 18 from the point of afiixation of its lower end to the frame member 15, as induced by the differential expansion of the lower end of the heater unit or the differential expansion of the heating unit relative to the frame member 15, is absorbed by the return of the deflected upper end of the heater unit to its normal undeflected position prior to its affixation to the frame member 15.

Therefore, by our invention we provide a heater unit which is designed to overcome the inherent structural deficiencies of conventional heater units which, when subjected to differential expansion caused in the above described manner, rupture and shear or tear away from their supporting frames. We accomplish these desirable ends by incorporating in the heater unit an expansion space which is dimensioned to accommodate differential expansion proportional to the size of the heater unit and to the extent to which it will be subjected to such differential expansion because of the capacity thereof.

Furthermore, the entire heater unit is so aifixed to its supporting frame member that it is placed under stress along its length so that, when differential expansion occurs in the unit due to the generation of heat therein, the unit is returned to its normal or approximately normal state in which it existed prior to its afiEixation to the frame member, subsequently returning to the stressed state when it has cooled sufficiently to restore it to equilibrium conditions.

We claim as our invention:

1. A heater comprising in combination: an upright frame member; an upright relatively tall and narrow heating unit comprising a relatively tall and narrow lower main portion including Walls forming an open-topped combustion chamber portion and an upright heat exchanger portion thereabove communicating with said open top to receive a column of products of combustion from said combustion chamber portion, the horizontal cross section of said column being wide in a direction at right angles to said frame member but narrow transverse to said direction, said heating unit being subject to greater heat expansion than said frame member, said walls of said combustion chamber portion and of said heat exchanger portion forming a relatively extensive upright front edge adjacent said upright frame member, said heating unit including a duct member joined to and communicating with said heat exchanger portion exclusively at a rear position substantially removed from said front edge to leave a shallow expansion space between said duct and said heat exchanger portion, said expansion space being disposed forwardly of such rear position, said duct member receiving products of combustion from said heat exchanger portion and conducting same to a forward end of said duct member; first means for fixedly attaching a forward portion of said combustion chamber portion adjacent said front edge to said frame member at a lower position; and second means for fixedly attaching said forward end of said duct member to said frame member at an upper position against vertical movement relative thereto, said first and second attaching means supporting at least a part of the weight of said heating unit.

2. A heater as defined in claim 1 in which said walls of said heating unit are formed of sheet metal sections having peripheral flanges secured together in a vertical mid-plane of said tall and narrow heating unit, a portion of said secured-together flanges forming said front edge, said sheet metal sections providing upright extensive-area side panels forming the opposite sides of said combustion chamber portion and said heat exchanger portion, said expansion space tending to prevent buckling of said heating unit and to accommodate said greater heat expansion thereof.

3. A heater as defined in claim '1 in which said forward end of said duct member is vertically displaced abnormally away from said forward portion of said combustion chamber portion when such forward end of said duct member is attached to said frame member, thus establishing in said heating unit a prestress which tends to be relieved as said greater heat expansion of said heating unit takes place.

4. A heater comprising in combination: an enclosure forming an upright air heating passage, said enclosure including an upright metal sheet having vertically spaced openings which increase in center-to-center spacing with thermal expansion of said metal sheet; an upright relatively tall and narrow heating unit in said air heating passage including extensive-area upright side walls bounding a lower combustion chamber portion and a superimposed heat exchanger portion receiving hot products of combustion therefrom, said combustion chamber portion providing a lower tubular attachment means, said heat exchanger portion including a flue providing an upper tubular attachment means, said heating unit including rigid but stress-deformable means spaced a substantial distance from said metal sheet and initially holding said lower and upper tubular attachment means spaced from each other a small fraction of an inch less than the spacing of said openings, said deformable means being suffi ciently deformable to accommodate spreading of such tubular attachment means by such small fraction of an inch to align with said openings; and means for securing said lower and upper tubular attachment means to said metal sheet in such alignment while thus spread to prestress said heating unit, said heating unit beingsubject to greater heat than said metal sheet upon burning of fuel in said combustion chamber to produce said products of combustion, such heating of said heating unit expanding same to relieve sai-d prestress, said lower tubular attachment means conducting combustion-supporting air through the lower of said openings to said combustion chamber portion, said upper tubular attachment means conducting products of combustion through the upper of said openings from said heat exchanger portion, at least a portion of the weight of said heating unit being supported by said metal sheet through said tubular attachment means.

5. A heater as defined in claim 4 in which said openings of said metal sheet are spaced many inches from each other, and in which said heat exchanger portion opens directly on said combustion chamber portion to receive products of combustion therefrom, said flue comprising a conduit means connected to the upper interior of said heat exchanger portion at a position substantially removed from said metal sheet, said conduit means being spaced from said heat exchanger portion forwardly of such position.

6. A heater comprising in combination: an enclosure forming an upright air heating passage, said enclosure including a forwardly disposed upright metal sheet bounding said air passage, said metal sheet having lower and upper openings spaced vertically apart a large number of inches; a heater unit in said air heating passage comprising walls forming an upright tall and narrow main portion of substantially rectangular shape when viewed in side elevation, said main portion providing an open-topped combustion chamber in its lower end and a heat exchanger chamber above such combustion chamber and communicating with such open top to receive products of combustion therefrom, said walls including a top wall bounding the top of said heat exchanger chamber; an elongated tubular duct providing rear and front portions; a short tubular flue portion rising rigidly from the upper rear portion of said heat exchanger chamber and being connected rigidly to said rear portion of said elongated tubular duct to transmit to the rear portion thereof said products of combustion, said short tu'bular flue portion supporting said elongated tubular duct at a position spaced a,79a,sao

--7 vertically above said top wall to provide between such duct and such top wall a relatively shallow expansion space extending forwardly toward said metal sheet; a lower tubular attachment means connecting saidheater unit to said lower opening of said metal sheet at a position opposite said combustion chamber, said tubular attachment means conducting combustion-supporting air to said combustion chamber through said lower opening of said metal sheet; and an upper tubular attachment means on said front portion of said tubular duct for connecting same to said upper opening to conduct the products of combustion through such upper opening.

7. A heater as defined in claim 6 in which said lower and upper attachment means are initially spaced from each other by said short tubular flue portion a small fraction of an inch less than the spacing of said openings, said flue portion and said tubular duct being sufl'iciently deformable to accommodate spreading of such attachment means by such small fraction of an inch to space said attachment means from each other a distance equal to the spacing of said lower and upper openings, and including means for securing said lower and upper tubular attachment means to said metal sheet while thus spread, thereby initially prestressing said heater unit, said heater unit being subject to greater heat than said metal sheet upon burning of fuel in said combustion chamber to produce said products of combustion, such heating of said heater unit expanding same to relieve said pre-stress.

8; A heatcr unit as defined in claim 6 in which said walls are formed of sheet metal and have peripheral flanges secured together ina plane substantially at right angles tosaid metal sheet, each sheet metal Wall forming one side of ,said combustion chamber, heat exchanger chamber, short tubular flue portion, and elongated tubular duct, one portion of said peripheral flanges forming the crest of said top wall and being spaced from a peripheral flange portion along the bottom of said elongated tubular duct to bound said relatively shallow expansion space.

References Cited in the file of this patent UNITED STATES PATENTS 165,712 Chace July 20, 1875 378,101 Miller Feb. 21, .1888 1,307,433 Beuckman et al June 24, 1919 1,727,177 Prentice Sept. 3, 1929 2,012,210 Williams Aug. 20, 1935 2,247,849 Ritter July 1, 1941 2,391,028 Miles Dec. 18, 1945 2,495,673 Erwin Jan. 24, 1950 2,682,867 Cartter July 6, 1954 2,697,420 Lloyd Dec. 21, 1954 2,715,399 Witt et a1 Aug. 16, 1955 

